To make a tomato pizza topping for a normal pizza, Jake uses 300g of tomatoes, 120g of onions and 75g of mushrooms. Jake wants enough sauce for a giant pizza, so he uses 900g of tomatoes. Jake has now made his giant pizza. He says, ‘I made three times as much sauce to cover the giant pizza as I do to cover a normal pizza, so the giant pizza is three times as big as the normal pizza.' Do you agree with Jake and explain your answer?

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?